when choosing a turbo as yourself what you wwnt from your car.
If you dont mind the lag and want over 400 bhp then the 3037 is the one to go for.
But if your looking for a quick responsive road car then the gt2871r or the gtrs would be a better choice. The gtrs is rated at 400ps and spools up very well.
The turbo you have will produce 1.4 bar no problem but will not hold it to the redline theres nothing wrong with it its just running out of steam.
You need to match your turbo choice to your engine to get the best results from the turbo. Have a word with the builder of the engine see what they reccommend.